The invention relates to apparatus for implementing corneal transplants, or keratoplasty, and more particularly to method and apparatus for accomplishing the removal of the transplant button from separated and stored corneal tissue excised earlier from the eyeball of a donor. The general field of the invention is shown by the following U.S. Letters Patent:
Kendall U.S. Pat. No. 378,449 (Feb. 28, 1888); Stewart U.S. Pat. No. 2,929,603 (Mar. 22, 1960) and Swope U.S. Pat. No. 3,058,471 (Oct. 16, 1962).
Conventionally, the donor corneal tissue is stored as part of the whole eye in a moist chamber at 4.degree. C. Such storage is possible only for twenty-four hours, within which time the recipient must be prepared for surgery to accept the corneal transplant button cut from the donor eye tissue using a trephine. The same trephine or one identical to it is used to remove the damaged corneal tissue from the recipient eye and the corneal transplant button is then sutured in place in the recipient eye. These surgical steps are normally accomplished under a microscope.
Newly developed storage methods for donor corneas enable the corneal tissue to be stored for much longer than 24 hours. Long-term and intermediate storage methods permit cornea storage for periods from one week to one year's time. The whole eye is not stored as previously, but just the corneal tissue which is separated from the sclera and the rest of the eye and stored in a container by itself. Storage is in the recipient's blood serum or in mineral oil at 4.degree. C. Alternatively, it may be placed in a nutrient media and frozen with liquid nitrogen. More recent developments utilize a tissue culture media (such as McCarey-Kaufman corneal bathing Media) at 4.degree. C to store the corneal tissue separated from the eye of the donor.
While long-term corneal tissue storage facilitates keratoplasty by being more adaptable to the recipient's needs in terms of health and timing, difficulties have prevented general use. For instance, competent surgeons have been reluctant to accept long-term stored corneal tissue as equal in quality to tissue obtained from the whole eye the day of separation from the donor body. Demonstrated success of keratoplasties using long-stored tissue has overcome this problem. Also, the conventional exacting surgical technique of trephining part way through the cornea while it is part of the donor eye and completing separation by scissoring an angle cut from the bottom of the trephine incision through the endothelium layer separating the cornea from the eye's anterior chamber, has not heretofore been practicable on corneal tissue removed from the eye. The endothelium, being a key to successful corneal transplant, must be protected from damage. Trephining the corneal button on stored separated tissue has therefore been done from the endothelium side against a support surface, precluding the preferred keratoplasty techniques, including preparation of an endothelium flap on the button to seal the recipient cornea aperture against leakage of the aqueous humor which is within the anterior chamber of the eye between the cornea and the iris. To operate with the endothelium layer against a work surface to achieve normal techniques harms that layer and thus inhibits effective transplant.
I have invented apparatus and process whereby separated corneal tissue stored for long periods of time, with the attendant advantages to the recipient of such storage, can be transplanted with accepted surgical techniques under a microscope without damage to the endothelium or other parts of the transplant button.